1. Field of the Invention
The present invention relates generally to surgery devices and methods. More particularly, the present invention relates to a cryotherapy device and method to treat, destroy or ablate a patient's abnormal tissues or lesions, e.g., for the ablation of cervical, precancerous lesions to prevent cervical cancer.
2. Description of the Related Art
Cervical cancer is the third most common cancer in the world. Moreover, eighty percent of all cervical cancer cases occur in the developing world. With approximately 500,000 new cases each year, cervical cancer is responsible for over 250,000 deaths per year, making it the second leading cause of death in developing countries. Many of these deaths are women in their late 30s and early 40s, thus compromising the health and well-being of the surrounding family. Indeed, this is especially true for the children of these women, who often fall behind in their education and may be abandoned, without a mother.
While steps, such as annual PAP smears and other interventional methods, have been taken to eradicate cervical cancer in the developing world, cervical cancer still remains a large burden for these countries. Its prevalence in the developing world can in large part be attributed to a lack of appropriated technologies for screening and treatment.
A “single visit” approach has been developed and includes a screening by visual inspection with acetic acid and a point-of-diagnosis cryotherapy treatment. This approach for screening and treatment has provided a safe, acceptable, and feasible option in low-resource settings.
Cryotherapy includes freezing the abnormal cervical tissue with a coolant such as carbon dioxide, CO2, and has been used for over forty years to treat cervical dysplasia. This process uses what is called a “double freeze procedure.” One freezes the cervix for three minutes and then allows it to thaw for five minutes, then it is frozen again for an additional three minutes. This procedure maximizes the amount of tissue that is frozen more so than just doing one extra-long freeze because the frozen tissue becomes more thermally conductive after the first freeze so the second freeze penetrates quicker and subsequently deeper into the affected tissue.
Cryotherapy is the leading method for the ablation of cervical precancerous lesions for the prevention of cervical cancer, especially in the developing world. Despite proven efficacy of cryotherapy as a mode of ablating precancerous lesions, the current state of the art used to facilitate cryotherapy is not sufficiently designed for widespread and reliable use in the developing world.
While this single visit approach or “screen and treat” program has been shown to be effective in prevention of cervical cancer, there still remains a hurdle to scaling up such a program for widespread impact. While cryotherapy using CO2 has been shown to be safe and effective, even in the hands of low-level health care workers, the equipment is not necessarily suitable to be widely dispersed. Indeed, cryotherapy tools can be expensive, technically complex, lacking portability, and difficult to repair in the field.
Currently, the developing world utilizes cryoguns, see, for example, U.S. Pat. No. 4,377,168 which discloses expanding pressurized CO2 (or N2O in some instances when a country or program can afford the added expense of the N2O) against a thermally conductive tip. The expansion of the CO2 in this closed system creates a temperature of approximately −50 to −70 degrees C. on the surface of the tip which is in contact with a lesion.
With carbonated beverage manufacturers being widely dispersed in the developing world, and often using carbon dioxide to produce their carbonated beverages, carbon dioxide manufacturers are also widely dispersed in the developing world. This has led to cryoablation being conducted with carbon dioxide as the primary source of coolant.
The current design of cryotherapy tools suffers from several flaws when utilized with carbon dioxide tanks, including: water vapor leaving the tank causes tip blockages, non-medical grade carbon dioxide may have particulates, which cause tip blockages, and a pressure drop may occur in the cylinder through the cooling process during extended use which results in warmer and less effective tip temperatures.
Additionally, the equipment was never originally designed for use within the extreme conditions of the developing world where there are high volumes of ablations along with environmental abuse of the product. First, the tips on the current cryotherapy tools are manufactured with gold or chrome plating, which not only makes the tip expensive, at approximately three hundred dollars per tip, but these tips also suffer from corrosion from the chlorine disinfection method—the widely available method for sterilization in the developing world.
Improper cleaning and storage of these tips also leads to clogs, requiring replacement. Additionally, the overall cost of the equipment is around thirteen hundred to two thousand dollars per device. Moreover, with the complexity of this equipment's engineering design, there is a lack of repair knowledge and backup parts when the equipment breaks down. Unfortunately, when the cryotherapy equipment malfunctions in the field, the device becomes unused and is rarely capable of being easily fixed.
Finally, the amount of carbon dioxide required per treatment limits the portability of the device. A tank containing 50 lbs of CO2, weighs approximately 160 lbs total, and treats only about 10 to 15 patients. These large tanks are therefore difficult to transport to the rural areas where women need to be screened and treated, either in the context of health centers, mobile health vehicles or organized screen & treat camps. Therefore, these characteristics of current cryotherapy equipment prohibit its massive scale-up for widespread impact on reducing the burden of cervical cancer.
It would therefore be advantageous to provide a device and method that could safely, effectively, and in a low-cost manner treat, destroy or ablate cervical, precancerous lesions in order to prevent cervical cancer.